Baseline variables that were gathered several months following IM, included autonomic symptoms, days in bed since IM, perceived stress, stressful life events, family stress, difficulty functioning and attending school, family stress, and psychiatric disorders.

A number of variables were predictors of post-infectious CFS at six months; however, when autonomic symptoms were used as a control variable, only days spent in bed since mono was a significant predictor.

Step-wise logistic regression findings indicated that baseline autonomic symptoms as well as days spent in bed since mono, which reflect the severity of illness, were the only significant predictors of those who met CFS criteria at six months.

I do hope Prof. Jason and his team continue this work into ME/CFS post IM. I would also be worth looking at other variables which may affect who goes on to develop ME/CFS after IM.

For example:
Vitamin D status.
Because vitamin D is immunomodulatory, those with low vitamin D levels at the time of infection will have a more severe form of the illness and since illness severity is the biggest predictor of ME/CFS perhaps vitamin D status is a predictor.

Low vitamin D status during childhood causes increased antibodies to thyroid and subsequent thyroid function. Most people with ME/CFS have some thyroid dysfunction and their symptoms reflect that. Poorer thyroid function during an illness such as IM would probably also result in higher severity of illness and consequently higher risk of ME/CFS